Most commercially available fluorinated acrylic polymers as as water/oil repellents or stain resist produced through electrochemical fluorination or telomerization. Electrochemical fluorination utilizes anhydrous hydrofluoric acid as the fluorine source. However, industrially produced hydrofluoric acid contains impurities; which requires further complicated methods to remove these impurities.
Telomerization processes use tetrafluoroethylene as the starting material. However, tetrafluoroethylene is expensive intermediate with limited availability. The telomerization products contain a mixture of homologs which contain a distribution of different carbon chain lengths. Therefore, in order to produce fluorinated surfactants which contain a fixed length of the fluorinated carbon chain, some sequential separation of telomerization products is required, as described by Erik Kissa in “Fluorinated Surfactants, Synthesis-Properties-Applications”.
For example, U.S. Pat. No. 7,101,924 discloses an acid treated, aqueous dispersion which provides oil and water-repellency comprising a polymer, at least one water-dispersible polyester, water and at least one acid-generating compound; wherein said polymer comprises repeating units from at least one fluoroalkyl monomer and optionally at least one ethylenically unsaturated monomer; wherein said fluoroalkyl monomer is a (meth)acrylate. The suitable substrate of aobve oil and water repellents described in '924 is selected from the group consisting of a yarn, thread, fiber, fabric, paper and carpet.
Historically, many repellents, such as described above in Examples in '924, contain perfluoroalkyl groups having 6 and above carbon chain length. For example, Koji Honda et al., in “Molecular Aggregation Structure and Surface Properties of Poly(fluoroalkylacrylate) Thin Films” Macromolecules (2005), 38(13), 5699-5705, teach that the orientation of the perfluoroalkyl chains of at least 6 carbons is maintained in a parallel configuration, while for such perfluoroalkyl chains containing 6 or less carbons, reorientation occurs. This reorientation decreases effects for altering surface behaviors.
Nevertheless, there is a disadvantage of using such fluorinated materials containing longer perfluoroalkyl chains since the high price of fluorinated material is determined by the amount of fluorine incorporated in compound. Therefore, it is desirable to obtain fluorinated repellents which can be prepared from fluorinated chemicals with short and exact chain length perfluoroalkyl groups. It is further desirable that such such fluorinated repellents with short and exact chain length perfluoroalkyl groups still provide essentially the same or even superior performance.
It is unexpectedly discovered in the present invention that a solvent based fluorinated methacrylic polymer which contains fluorinated groups having exact 6 carbon chain length can provide the desired oil and water repellency, and stain resistance properties to the treated substrates including leather, and hard surface substrates.
Furthermore, conventionally in fiber treatment applications, the fluoroalkyl(meth)acrylate monomer is copolymerized with at least one ethylenically unsaturated monomer such as a methacrylate or acrylate as described in '924. The fluorinated methacrylic polymer in the present invention is prepared by the copolmerization of repeating units from at least one fluorinated methacrylic monomer and at least one non-fluorinated acrylate. It is unexpectedly discovered that the non-fluorinated acrylate is preferred, and non-fluorinated methacrylate is particularly excluded in this invention in order to render the solvent based fluorinated methacrylic polymer desired oil and water repellency, and stain resistance properties to the treated substrates including leather, and hard surface substrates.